package cn.fyl.first;
public class Stack {
private ArrayList elementData = new ArrayList();
int last;
public void push(Object o) {
elementData.add(o);
}
public Object pop() {
return elementData.remove(last-1);
}
public Object peek() {
last = elementData.size()-1;
return elementData.get(last);
}
public boolean isEmpty() {
if(elementData.size() > 0)
return false;
else
return true;
}
public int size() {
return elementData.size();
}
public static void main(String[] args) {
Stack s = new Stack();
s.push(1);
s.push(2);
s.push(3);
System.out.println(s.peek());
}
}